Spectroscopic Identification of the Infrared Counterpart to GX5-1

Bandyopadhyay, R. M.; Shahbaz, T.; Charles, P. A.
Bibliographical reference

American Astronomical Society, 201st AAS Meeting, #54.07; Bulletin of the American Astronomical Society, Vol. 34, p.1199

Advertised on:
12
2002
Number of authors
3
IAC number of authors
1
Citations
0
Refereed citations
0
Description
Using CGS4 on UKIRT, we have obtained a 1.95-2.45 micron infrared spectrum of the primary candidate counterpart to the bright Z low-mass X-ray binary (LMXB) GX5-1. IR photometry by Naylor, Charles, & Longmore (1992) and the astrometry of Jonker et al. (2000) had previously identified this star as the most likely counterpart to GX5-1. The spectrum presented here clearly shows Brackett γ and He lines in emission, for the first time confirming the identity of the counterpart. Similar to our previous spectroscopy of the Z LMXBs Sco X-1 and Sco X-2 (Bandyopadhyay et al. 1999), the K-band spectrum of GX5-1 shows emission lines only, possibly indicating that the spectral type of the mass donor is earlier than G5. We discuss the implications of this spectrum for the nature of the Z LMXBs.